These studies are investigating lead (Pb) toxicity at chronic doses generally be low those producing overt clinical symptoms of Pb poisoning. Pb has been administered at various developmental states (in utero, during year 1 postpartumor to adult animals). Measures of Pb dosages include daily Pb intake, blood Pb level, and zinc protoporphyrin concentration. Measures of clinical effects include assessments of general health, appetite, and hematocrit. The primary focus of the project is on measures of behavioral toxicity, particularly long-term behavioral deficits. We have observed Pb-induced alterations in scoptic visual ability, discrimination reversal learning, a spatial memory task, activity functions, and social behaviors. Most deficits have been replicated at more than one Pb dosage condition and some have been seen several years after termination of early Pb exposure. These behavioral functions will be further investigated in monkeys of different Pb exposure conditions to attempt to establish (i) the determining variables producing the impairment (e.g., developmental stage of Pb exposure, dosing duration, Pb intake, PbB) and (ii) the extent to which the impairments endure beyond the period of Pb exposure. In addition, tests of these behavioral functions will be further developed to facilitate characterization of the nature of the Pb-induced deficits. Finally, selected animals will be sacrificed to study Pb distribution in body tissue (including regional analyses of Pb in brain) as well as to study Pb-induced neuroanatomic lesions.